Compressors and systems incorporating compressors have been developed and are often utilized in a myriad of industrial processes (e.g., petroleum refineries, offshore oil production platforms, and subsea process control systems). Conventional compressors may be configured to compress a process fluid by applying kinetic energy to the process fluid to transport the process fluid from a low pressure environment to a high pressure environment. The compressed process fluid discharged from the compressors may be utilized to efficiently perform work or operate one or more downstream processes. Improvements in the efficiency of conventional compressors has increased the application of the compressors at various oil production sites. Many of the oil production sites (e.g., offshore), however, may be constrained or limited in space. Accordingly, there is an increased interest and demand for smaller and lighter compressors, or compact compressors. In addition to the foregoing, it is often desirable that the compact compressors be capable of achieving higher compression ratios (e.g., 10:1 or greater) for increased production while maintaining a compact footprint.
To achieve the higher compression ratios, conventional compact compressors may often utilize an impeller and a balance piston integrally formed with the impeller. The impeller may be configured to rotate within the compact compressors to accelerate the process fluid, and the integral balance piston may be configured to balance axial thrusts generated by the rotation of the impeller. As the impeller rotates to accelerate the process fluid, however, at least a portion of the process fluid may leak or flow pass the impeller and the balance piston (e.g., via radial clearances), thereby reducing the efficiency of the compact compressors.
In view of the foregoing, conventional compact compressors may often utilize balance piston seals (e.g., hole pattern seals) to manage the leakage flow of the process fluid. However, as the impeller accelerates to the rotational speeds necessary to achieve the higher compression ratios (e.g., 10:1 or greater), thermal energy (e.g., heat of compression) and/or centrifugal forces may cause the impeller and the balance piston to expand or grow at a relatively increased rate relative to the stationary balance piston seal. The relatively increased rate of expansion exhibited by the impeller and the balance piston integrally formed therewith may often result in decreased operational efficiencies, and may ultimately result in damage to the compact compressors and/or components thereof. For example, radial and/or axial growth of the impeller and the balance piston may correspondingly decrease or eliminate clearances (e.g., radial clearances) between the balance piston and the balance piston seal, thereby resulting in damage from the incidental contact between the balance piston and the balance piston seal.
What is needed, then, is an improved balance piston seal assembly for a compact compressor having relatively high compression ratios.